Synchronous optical network in frequency domain

Abstract

An optical wavelength add/drop multiplexer provides communications between two optical links supporting wavelength division multiplexing (WDM). A wavelength slicer spatially separates the input signal into two sets of channels. An optical filter, such as an interference filter, spatially separates the a subset of the input channels into an array of separated channels. A programmable optical add/drop switch array selectively routes channels from and array of input ports to an array of drop ports, substitutes channels from an array of add ports in place of the dropped channels, and routes the remaining input channels and added channels to an array of output ports. The channels from the output ports of the said add/drop switch array are then combined and transmitted into the second optical link. In an alternative embodiment, a circulated drop filter consisting of an optical circulator and a series of filter Bragg gratings is used to select a predetermined series of input channels to be processed by the add/drop switch array, with the remaining channels being passed by the circulated drop filter as express lanes.